Let’s start with something on which everyone should agree: metrics are neither inherently good nor inherently evil. They are simply calculations — ticks on a stick that measure time, distance, speed, place, or other attributes. All measurements can be used well or poorly and most disagreements are not about the number, but about the use.
For many years education metrics were predominantly based on proficiency: how close is a student to a specific standard. However the misunderstanding and misuse of proficiency metrics have led to a number of consistent abuses: assigning relevance to trends over time using different cohorts (e.g. this year’s 6th grade vs. last year’s 6th grade) or discrete standards (3rd grade math compared to 10th grade math). In particular, many users of proficiency data commit the cardinal sin of comparing the performance of schools with vastly different demographics.
The new favored metric in education is growth percentiles (which measures change in an individual student or cohort over a year’s time). And the ability to measure student growth is a significant milestone and provides an incredible amount of value and insight. Growth percentiles are also adjusted to group students with similar academic histories, making comparisons far more valid. But, like proficiency before it, growth is often misunderstood and misapplied, and is routinely cited as evidence for conclusions that it does not support.
My criticism here is not the metric, it is how the metric is being used (and my comments are limited to the Colorado Growth Model, where “growth” as commonly used refers to median growth percentiles). Here are some of the primary issues with the use of growth percentiles in Colorado.
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Ooms With A View 